As an increasing number of electronic appliances such as video or audio apparatuses or PCs have been used in a home and digital techniques have become dominant in video and audio signal processing, the need for communication among home electronic appliances or communication with other networks is also increasing. In addition, the demand for controlling home electronic appliances through a single apparatus such as a PDA is also increasing.
To meet the demand, home networking technology has emerged for connecting home electronic appliances such as digital TVs or DVD players. The UPnP (Universal Plug and Play) is a key technology required for implementing the home network.
According to the UPnP specification, every home network requires an apparatus, which handles data arbitration among elements (or nodes) connected to the network and assigns addresses to the elements. The apparatus also acts as a gateway to a public network by using a public IP address, e.g., network address of the Internet, thereby enabling home network appliances to communicate with the Internet. The apparatus is called IGD (Internet GateWay Device), which can be a stand-alone device or embedded within another apparatus such as a PC or refrigerator.
Each device connected to a home network, in order for efficient utilization of limited public address resources, uses one of private IP addresses assigned arbitrarily to a home network instead of using a separate public IP address for each device.
Instead of watching particular contents stored in a particular device (e.g., HTTP-based media server) by using a device on a home network, the user of a home network may want to watch contents stored in the media server remotely from outside. However, since each device connected to a home network, for the purpose of efficient utilization of limited public address resources, uses a private IP address assigned arbitrarily to the home network instead of using a separate public IP address for each device, access to the home network from outside is impossible.
One possible method to enable access from outside may be to use an NAT (Network Address Translation) module within IGD for port mapping, thereby providing mapped URLs. The above method brings about inconvenience that separate URLs should be prepared both for access from a device within a home network and from an external device. Since separate URLs are dynamically created and assigned to respective contents managed by a media server, it is infeasible to realize a method for enabling access from outside via mapping by the NAT module.
Another method can use a VPN (Virtual Private Network) client; when a VPN server is installed on a device carrying out a function of a gateway such as IGD and a VPN client is executed from a remote device to establish connection, the remote device is assigned a private IP address belonging to the range of private IP address managed by a gateway device, thereby becoming a virtual device on the home network and being able to make access to a media server with a private IP address. Since the above method, however, allows a remote device to make access to all the devices on a home network via a VPN client, security thereof should be considered.